Check if the user uses --firstParty. (#3643)
Check if the user uses --firstParty. (#3643)

This catches if the user use --firstParty but actually
do not match any requests.

https://github.com/sitespeedio/sitespeed.io/issues/3642
sitespeedio/sitespeed.io,sitespeedio/sitespeed.io,sitespeedio/sitespeed.io,sitespeedio/sitespeed.io